NRC says nuclear plant hole should have been found earlier

By JOHN SEEWER
The Associated Press
4/5/02 11:44 AM

OAK HARBOR, Ohio (AP) -- An acid leak that ate through a steel cap over a nuclear plant's reactor vessel should have been spotted as many as four years ago, according to a Nuclear Regulatory Commission report released Friday.

Inspectors said there were many opportunities for the operator of the Davis-Besse plant to find the problem, which wasn't discovered until the plant was shut down in February for refueling.

"It should have been recognized," said NRC spokesman Jan Strasma.

Plant employees found leaking boric acid created a 6-inch hole in the steel cap near a cracked control rod nozzle. The hole was stopped by a steel layer, three-eighths of an inch thick, that is impervious to the acid.

The NRC said it was the most extensive corrosion ever found on top of a U.S. nuclear plant reactor. Inspectors spotted a second cavity 1 3/4 inch deep two weeks later.

The agency said the damage did not pose a safety threat. However, the agency ordered operators of all 69 pressurized water reactors in the United States to submit information on the structural integrity of their plants' reactor heads.

The NRC is still reviewing data submitted by those nuclear plants but has found nothing so far that indicates further problems, Strasma said on Friday.

The NRC report was released at a public meeting attended by hundreds of residents. About a dozen opponents of the plant held up signs that said "No nuclear time bombs" and interrupted the meeting several times by yelling "You failed" and "Shut it down."

Plant opponents told an NRC official that Davis-Besse should be shut down immediately.

"Is it going to take a meltdown?" asked Joyce Pryke, who lives just a few miles from the plant.

Significant corrosion began at least four years ago, according to preliminary findings of an NRC inspection. Inspectors said it was caused by cracked control rod nozzles.

Davis-Besse employees should have recognized that clogging in an air cooler and radiation monitor filter were signs of the corrosion, said Mel Holmberg, an NRC inspector. Workers also failed to clear several inches of the rust-colored boric acid that was building up on the reactor head, he said.

The plant had "several opportunities to find the corrosion and failed to do so," Holmberg said.

Akron-based FirstEnergy Corp. operates the plant.

Howard Bergendahl, a company vice president in charge of Davis-Besse, acknowledged that the problem should have been discovered earlier.

"We could have and should have found it in earlier inspections," he said.

The plant was inspected over the years, but corrosion was overlooked because plant staff and management for years did not realize the significance of boric acid deposits on top of the vessel head, according to a report prepared by FirstEnergy and sent to the NRC.

The company said similar corrosion can be found or avoided at similar plants if engineers know to look for it.

The acid is a byproduct of the nuclear fission process inside the reactor. The reactor has 69 control rods. The nozzles are vertical tubes that house the rods, which absorb excess neutrons in the reactor core.

The damage to the reactor's steel cap will keep the plant shut down until at least June. The plant is along Lake Erie and about 25 miles east of Toledo.

FirstEnergy plans to install a new reactor head during the plant's next refueling shutdown in 2004. The company said a new reactor cannot be installed now because it will take months to build.

FirstEnergy will tell regulators next week about its plans to repair the original reactor head. The plan will need NRC approval.

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On the Net:

http://www.nrc.gov

http://www.firstenergycorp.com